Low concentrations of thymidine modulate allogeneic responses

Abstract

The effect of the addition of low concentrations of thymidine on the development of primary allogeneic immune responses in culture was studied. It was found that, dependent upon day of addition to culture, allogeneic cytotoxic T-lymphocyte generation was augmented by thymidine in the concentration range of 10 −9 to 10 −8 M, while specific T-suppressor cell development was inhibited by 10 −7M thymidine. Based on the concentration of thymidine in serum, its addition in the concentration range of 10 −9 to 10 −7M results in 0.1 to 10 fold concentration change in cultures supplemented with 10% serum. While the mechanism(s) by which such minor changes in thymidine concentrations induced the modulations seen have not been elucidated, it is clear that such changes are easily attainable. In fact, such variations in the concentration of thymidine could contribute to the variable results often observed with different lots of fetal calf serum and workers investigating immunomodulations in culture systems should be aware of this possibility.